Saturday, 15 September 2012

Fireworks recorded using GH2 and Samyang 7.5mm f/3.5 fisheye

It was very dark during this firework, so to record it, I had to push the exposure as high as possible. I used the "Creative Movie Mode", with the manual setting ("M"), in which I could dial in ISO 3200 (the maximum), and used the largest aperture on the Samyang 7.5mm fisheye lens: f/3.5.

A little known feature of the Panasonic GH1 and GH2 is that you can record videos with a slower shutter speed than the frames per second setting. I was using the high bit rate 25 fps 1080p mode, and to get sufficient exposure, I set the shutter speed to 1/13s, i.e., slower than 1/25s. This is possible only in the "Creative Movie Mode", in the "M" exposure mode, and with autofocus turned off. Of course, you don't actually get 25 frames per second with a shutter speed of 1/13s, you only get 13 frames per second.

To make the video clip more interesting, I speeded up the video to 200% speed, meaning that the frames per second of the output clip was about 25fps.

I also changed the tempo of the sound, to keep it in sync with the 2x fast video.

Conclusion

The Samyang 7.5mm f/3.5 fisheye lens is very good for recording fireworks. But to get sufficient exposure, you may need to set the shutter speed quite low, lower than 1/30s, giving you fewer frames per second than you are used to. This feature of the Panasonic GH1, GH2 and GH3 cameras is quite useful, and I don't think other Micro Four Thirds cameras can record videos with this slow shutter speeds.

When the GH3 gets released soon, I would guess that it can record videos at ISO 6400, which may solve this issue.

I have verified that this trick works perfectly on the G6, further confirming that it was intended as the GH2 replacement. The GM1 cannot do this trick with the kit zoom mounted, but it can do it with an adapted MF lens mounted. Go figure ...